The present invention relates generally to processing tubing and, more particularly, is concerned with a system for processing both ends of tubes, such as nuclear fuel rod cladding tubes.
An operational step in the nuclear fuel fabrication process is the manufacture of fuel rod cladding tubes. Such tubes typically are made of a zirconium alloy and have a length between about eight and twelve feet, an outside diameter of about 0.374 inch, and a thickness of about 0.023 inch. These tubes are loaded with uranium-containing nuclear fuel pellets and sealed at both ends with end plugs. The loaded tubes, now called nuclear fuel rods, are grouped into fuel assemblies which are loaded into the core of a nuclear reactor. A liquid moderator/coolant, such as water, is pumped through the core of the reactor and directed to pass along the fuel rods of the fuel assembly in order to extract heat generated therein by the fuel pellets for the production of useful work, such as the generation of electrical power.
During the manufacture of a fuel rod cladding tube, the tube ends undergo various processing steps. For example, each tube end may be deburred, each tube end may be flared, one end may be connected to a debris-collecting nozzle while the other end is subjected to a blast of compressed air to blow-out the tube, a manifold may be connected to each end for a flush-etching operation using an acid followed by a water rinse to size and clean the tube inside surface, nozzles may be connected to each end to pass dry air through the tube, and plugs may be temporarily inserted into each tube end for the tube to undergo an underwater ultrasonic inspection, etc. The cladding tubes are normally processed in batches or sets with tubes having the same length within a set. Control rods and burnable absorber rods, which also are used in nuclear reactors, have tubes whose ends undergo similar processing operations. Cladding tubes become fuel rods with additional tube-end processing steps including: inserting and girth welding an end plug to one tube end, loading fuel pellets into the tube from the open tube end, inserting and girth welding an end plug to the open tube end, internally pressurizing the tube through a hole in one end plug, seal welding the pressurization hole, and inspecting the welds. Other end processing procedures are possible for tubes used in diverse applications.
An important consideration during the manufacture of nuclear fuel rods is avoiding excessive tube flexing. To prevent fuel pellet damage, a loaded fuel rod must be supported and moved such that it is kept straight within specified tolerances. An excessively flexed fuel rod must be rejected.
Typical tube end processing systems transversely move the tubes between tube-end-processing stations using conveyors, such as walking beams. A tube then is longitudinally moved to and from a tube-end-processing machine, usually by rollers. Different length tubes are accommodated since such systems do not simultaneously process both ends of a tube.
U.S. Pat. No. 4,300,672 discloses improved apparatus for fabricating tubing which accommodates different length tubing and which can be used to simultaneously process both ends of a tube. In that patent, a conveyor and the tube-end-processing machines for one tube end are mounted on a fixed module, and a conveyor and the tube-end-processing machines for the other tube end are mounted on a movable module (to accommodate different length tubing).
What is needed is a tube-end-processing system which can accommodate different length tubing and simultaneously process both ends of a tube while having the versatility to accept different tube-end-processing machines into the system and all without excessive tube flexing and without the need for a massive structure to support a line of machines for one tube end and to support and move (to accommodate different length tubing) a line of machines for the other tube end.